The present invention relates to a locking device for covers, gratings and lids for gullies, manholes, shafts, etc., which device includes a locking means operable from the upper or outer side of the cover so as to engage with the wall of the well inside the cover.
Covers over gully holes, manholes for culverts and wells are normally allowed to rest freely in place in the hope that unauthorized persons will be unable to open the cover because of its weight and cumbrousness. However, a great number of accidents in which people have fallen down in wells and manholes has shown that there is a need for an effective and reliable locking mechanism. One prior art proposal is that relatively small covers should be provided with hooks which could by snap action be brought to engage with corresponding hooks provided on the brim of the well. Locking bolt devices have also been proposed in the art, the brim of the well being provided with recesses which these devices could be caused to enter for the purposes of locking the cover. These prior art apparatuses have not gained any appreciable commercial success, the reason supposedly being that they have complicated the manufacture of the covers, or that the locking mechanism has been put out of operation by rust or dirt.